Many spot and flood lamps are manufactured using a thin film of reflective aluminium deposited on the inside of the glass. Unlike dichroic reflectors, this reflects both light and heat forwards out of the lamp.

Part of a fluorescent lamp fitting which regulates the current flow through a fluorescent lamp.

See cap.

Specialist fluorescent lamp designed to emit invisible ultraviolet (UV) light.

A popular term for the electric lamp, derived from the bulb-shaped glass envelope in which lamps are often enclosed.

The burning position defines the position in which lamps should be installed and operated and are sometimes defined by code letters as follows:-

• h = vertical (base upwards)
• s = vertical (base downwards)
• p = horizontal

The candela (cd) is a standard measure of luminous intensity to allow direct comparison of the “brightness” of different light sources. For any physicists who may be reading this:-

“The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 x 1012 Hertz and that has a radiant intensity in that direction of 1/683 Watt per steradian.”

Bayonet (BC/B22) cap and
Edison Screw (ES/E27) cap

The electrical connection and mechanical fixing for a lamp is often referred to either as a cap or base. Lamps use a wide variety of fittings, partly to meet the appropriate electrical and safety requirements and partly to ensure that luminaires can only accept the appropriate lamp (eg to prevent using low voltage lamps in mains fittings). Common caps for standard incandescent lamps include the ubiquitous 22mm “bayonet” fitting (otherwise known as “B22d” or “BC”) and the Edison Screw (or “ES”) fitting, named after the early pioneer in electric lamp development. To ensure compatibility between different manufacturers’ products, international standards for lamp bases have been agreed by the IEC under the IEC 60061 standard. For further information see the caps and bases page.

The colour temperature of a lamp is a measure of the “warmth” or “coldness” of the light that it produces. Lamps that produce a “warm” or “yellowish” light (for example the sodium lamps used for street lighting which appear orange) have a low colour temperature. Lamps producing a pure white or bluish tinged light have a higher colour temperature.

Colour temperature is measured in degrees Kelvin (K) and is defined as “the temperature of a black body having the same colour appearance as the type of lamp being considered”.

• Lamps with a colour temperature of less than 3500K are usually described as having a “warm” appearance
• Lamps with a colour temperature between 3500 and 5000K are considered to have a “cool” appearance,
• Lamps having a colour temperature over 5000K are said to have a “cold” appearance.

Typical colour temperatures are:-

• High pressure sodium lamps: 2000K to 2200K
• Tungsten filament light bulb: 2700K
• Tungsten halogen lamps: 3000K
• Fluorescent lamps: 2700K to 6500K
• Metal halide lamps: 3000K – 5600K
• Daylight: 5500 – 6500K
• LED bulbs 3000K-6500K

Also known as “crown silvered” lamps, these are incandescent lamps with a highly reflective coating on the front of the glass. This reflects much of the light back towards the lamp fitting.

Originally designed for use in spotlight fittings with parabolic reflectors, particularly for shop window displays, these are also used in many contemporary “designer” light fittings to reduce glare and create spectacular effects where the lamp itself is visible.

Since the reflective coating also reflects heat back in to the luminaire, these lamps can cause overheating and should only be used with luminaires that have been designed to accept them. Search for bulbs matching Crown Silver.

Integrated and Non-integrated
compact fluorescent

Often also known as “Low Energy” bulbs, compact fluorescents use the same technology as fluorescent tubes but with the tubes “folded” into a much more compact design. The main advantages of compact fluorescents are:-

• Lower power consumption – typically 80% less than equivalent incandescent lamps.
• Longer operating life – typically 3 to 15 times longer than conventional incandescent lamps.
• Lower heat output than incandescent lamps, making them ideal for use in enclosed fittings or close to delicate lampshades.

There are two distinct categories of compact fluorescents:-

• Integrated: The lamp includes both the fluorescent tube and the necessary control gear in one package. These are ideal for use in direct replacement for conventional incandescent lamps and are often produced with standard BC or ES fittings.
• Non-integrated: The control gear is part of the fitting or luminaire and the lamp is just the folded tube. These used to be fitted mostly in commercial and industrial fittings but are more frequently now being used in homes as well as in exterior lighting.

Search for compact fluorescents in the product database.

Fluorescent lamps require special circuits to start the lamp when power is applied (the starter) and then to limit the electrical current once it is running (the ballast). This is often referred to as the control gear. In conventional fluorescent fittings, the ballast is integrated into the light fitting and the starter is generally a small user-replaceable plug-in tubular component.

In “high frequency” or “electronic” fluorescent fittings, the control gear uses an electronic circuit to perform these functions. This makes the lamp faster to start, more efficient and virtually flicker free. In some compact fluorescent fittings, this circuitry is fully integrated into the lamp itself.

Certain types of electronic control gear also allow fluorescent tubes to be dimmed.

See Chrome Cap.

Dichroic reflector lamp

Sometimes known as “cool beam” lamps, dichroic lamps have a special multi-layer coating on the reflector of the lamp.

This means that visible light is reflected forwards whilst the heat is transmitted backwards through the rear of the lamp. The word “dichroic” literally means “two coloured”.

Lumena stock dichroic lenses which often appear to have a different colour around the edge. This is due to refraction of light at detailed above.

The filament is the part of an incandescent lamp that glows as an electrical current is passed through it. In very early lamps the filament was made of carbon. Most incandescent lamps now use tungsten filaments.

Fluorescent lamps are a type of gas discharge lamp which generate invisible ultra-violet radiation and then use a phosphor coating on the inside of the lamp glass to convert this into visible light using a process known as “fluorescence”. By using different coating materials, fluorescent lamps can be made to generate light in a range of different colour temperatures. Typically these include Warm White, White, Cool White and Daylight versions.

The tube diameter is often expressed in eighths of an inch (e.g. T5 = 5/8” = 16 mm).

Advantages of fluorescent tubes include:-

• High energy efficiency
• Long operating life (typically over 10,000 hrs)
• Even light distribution.

Some fluorescent lamps are manufactured without the fluorescent coating and use a bluish black glass in order to deliberately emit only light in the ultra-violet (UV) spectrum. These are used for specialist applications such as banknote forgery detectors and nightclub special effects lighting.

Fluorescent lamps are generally designed to work directly from the mains (110 or 240V AC power) but require a starter and ballast or electronic gear to operate. Electronic control gear (ECG) converts mains power to a very much higher frequency and gives several advantages over conventional ballasts and starters including:-

• Greater efficiency and hence lower power consumption.
• Reduced flickering
• Faster starting

Usually manufactured in a tube shape, fluorescent lamps can also be found in circular, “U”-shaped and a variety of other specialist shapes.

See Tungsten Halogen

See fluorescent lamps.

The International Electrotechnical Commission (http://www.iec.ch/) is the authoritative worldwide body responsible for developing consensus global standards in the electrotechnical field. IEC is dedicated to the harmonization and voluntary adoption of these standards, supporting the transfer of electrotechnology, assisting certification and promoting international trade.

Lamp is the generic term for a light source. Light bulbs, tubes, capsules and spots are all types of lamp.

Light Emitting Diode. LED’s are now widely used in the latest lamp technolgy. Typically emitting as much as 10 times the light per watt as a Halogen Bulb. Output can be as much as 100 lumens per watt or more. The best low energy light source available.

Many different types of lamp may be manufactured in “long life” versions. The design often means using better quality components, different construction and manufacturing techniques as well as more stringent quality control. Long life is a relative term and depends very much on the technology of the lamp as shown in the table below.

LED lamps life can vary from 10,000 hours upto 30,000. previously up to 50,000 hours was quoted but that is now regarded as optomistic.

See compact fluorescent and LED.

The standard unit of measurement used to measure the total light energy emitted by a source, based on the Candela. Often used to describe the brightness, the rule to remember is the higher the lumen output, the brighter the light will be.

Luminaire is the general term for the fitting into which a lamp is installed. This will always include a lamp holder with the electrical connection to the lamp and may also include shades, reflectors or diffusers along with decorative, protective and/or safety features.

Luminous Flux is the measurement of visible light emitted from a unit over wavelengths visible to the human eye, used to describe the brightness of light emitted from a source. Often confused with Radiant Flux, it is important to understand the difference of the two. Luminous flux is adjusted (weighted) to the sensitivity of the human eye, whereas radiant flux measures the total power of all light emitted and is not adjusted. Luminous efficacy is the ratio of total luminous flux to radiant flux.

Halogen capsule lamp and Tungsten halogen capsule encapsulated in a glass outer bulb.

Tungsten halogen lamps are similar to incandescent lamps but instead of just being filled with inert gas they also have small quantities of halogens (bromine, chlorine and iodine) or their compounds added to the filler gas and use quartz instead of glass for the lamp capsule. Benefits of tungsten halogen lamps include:-

• A slightly higher colour temperature than ordinary tungsten incandescent lamps, giving a bright, white light, ideal for shop display lighting.
• Physically much smaller than equivalent tungsten incandescent lamps.
• Longer rated life – typically 2000 to 5000 hours or more.

One disadvantage of tungsten halogen lamps is that the quartz envelope is much more sensitive to contamination than ordinary glass bulbs. The quartz capsule must not be touched with bare hands since contamination can lead to overheating and severely reduced life. Some designs get around this by encapsulating the lamp inside a glass envelope.

See Control Gear for Fluorescent Lamps.

Metal halide lamps are a type of discharge lamp that creates an electrical arc inside a high-pressure gas capsule containing various rare earth compounds. Usually used in retail, showroom and factory applications, they can create a very crisp white light with colour temperatures ranging from 3000 to 10,000°K.

Named after James Watt, the inventor of the steam engine, the Watt (W) is a standard international unit of measurement of power. In the case of electric lamps, the “wattage” of the lamp defines the amount of electrical power that it consumes and also is related to the brightness of the lamp. However since different types of lamp are more or less efficient in converting electrical power into light, the Watt is not in itself a measure of brightness. For example, a 20W compact fluorescent lamp is approximately as bright as a 100W incandescent lamp yet it consumes only one fifth of the power.